Hydraulic motor vehicle brake system and method for operating same

A hydraulic motor vehicle brake system, comprising:

• a first functional unit having
• at least one first hydraulic pressure generator, which is designed to build up a hydraulic pressure at a wheel brake;
• and
• a first hydraulic fluid reservoir, from which the first hydraulic pressure generator can draw in hydraulic fluid;
• and
• a second functional unit having
• at least one second, electric hydraulic pressure generator, which is controllable in order to build up a hydraulic pressure at the wheel brake;
• a check valve;
• at least one second hydraulic fluid reservoir, having an outlet, via which the second, electric hydraulic pressure generator can draw in hydraulic fluid, and an inlet, relative to which the check valve is arranged upstream in such a way that it has a blocking effect toward the inlet in respect of a flow direction;
• a device for opening the check valve when the second hydraulic fluid reservoir reaches a predetermined filling level during an intake process of the second, electric hydraulic pressure generator or the second, electric hydraulic pressure generator begins an intake process at a predetermined filling level, with the result that the second, electric hydraulic pressure generator can draw in hydraulic fluid through the second hydraulic fluid reservoir and via the opened check valve;
• a third hydraulic fluid reservoir arranged in series with the second hydraulic fluid reservoir between the first functional unit and the second, hydraulic pressure generator, wherein the check valve is arranged in a hydraulic path between the inlet of the second hydraulic fluid reservoir and an outlet of the third hydraulic fluid reservoir, thus enabling the second, electric hydraulic pressure generator to draw in hydraulic fluid from the third hydraulic fluid reservoir through the second hydraulic fluid reservoir and via the opened check valve;
• and
• a second check valve subject to a spring force at an inlet of the third hydraulic fluid reservoir.